Solder-precipitating composition and mounting method using the composition

Abstract

PCT No. PCT/JP94/02047 Sec. 371 Date Aug. 2, 1995 Sec. 102(e) Date Aug. 2, 1995 PCT Filed Dec. 6, 1994 PCT Pub. No. WO95/15834 PCT Pub. Date Jun. 15, 1995The invention provides a solder-precipitating composition containing Sn-Pb alloy powder and an organic acid salt of Pb as essential components, and capable of precipitating solder as a result of substitution between Sn contained in the Sn-Pb alloy powder and Pb contained in the organic acid salt of Pb. Further, the invention provides a mounting method including the steps of supplying a conductor on a board with a solder-precipitating composition which contains Sn-Pb alloy powder and an organic acid salt of Pb as essential components, heating the solder-precipitating composition supplied on the conductor, to precipitate solder on the conductor and pre-coat the conductor with solder, as a result of substitution reaction between Sn in the Sn-Pb alloy powder and Pb ions in the organic acid salt of Pb, mounting a device on the solder pre-coated conductor, and melting the solder layer to securely mount the device on the conductor.

We claim: 
     
       1. A solder-precipitating composition containing Sn-Pb alloy powder and an organic acid salt of Pb as essential components, and capable of precipitating solder as a result of substitution reaction between Sn contained in the Sn-Pb alloy powder and Pb ions contained in the organic acid salt of Pb. 
     
     
       2. The solder-precipitating composition according to claim 1, further containing a solvent and a viscosity-holding agent. 
     
     
       3. The solder-precipitating composition according to claim 1, wherein the content of the Sn-Pb alloy powder is 20-70 wt %, and the content of the organic acid salt of Pb is 7.5-50 wt %. 
     
     
       4. The solder-precipitating composition according to claim 1, wherein the precipitated solder has a eutectic structure of Sn and Pb, the Sn-Pb alloy powder contains 65-90 wt % Sn, and the content of the Sn-Pb alloy powder is 20-70 wt % of the solder-precipitating composition. 
     
     
       5. The solder-precipitating composition according to claim 1, wherein the Sn-Pb alloy powder has a particle size of 1-20 μm. 
     
     
       6. A solder-precipitating method comprising the steps of: supplying a solder-precipitating composition which contains Sn-Pb alloy powder and an organic acid salt of Pb as essential components; and   heating the solder-precipitating composition to precipitate solder as a result of substitution reaction between Sn in the Sn-Pb alloy powder and Pb ions in the organic acid salt of Pb.   
     
     
       7. The method according to claim 6, wherein the heating temperature is 210°-220° C. 
     
     
       8. A mounting method comprising the steps of: supplying a conductor on a board with a solder-precipitating composition which contains Sn-Pb alloy powder and an organic acid salt of Pb as essential components;   heating the solder-precipitating composition supplied on the conductor, to precipitate solder on the conductor and pre-coat the conductor with solder, as a result of ion substitution reaction between Sn in the Sn-Pb alloy powder and Pb ions in the organic acid salt of Pb;   mounting a device on the solder pre-coated conductor; and   melting the solder layer to securely mount the device on the conductor.   
     
     
       9. The method according to claim 8, wherein the heating temperature for precipitating solder is 210°-220° C.